INDUSTRIAL MINERALS IN ARIZONA’S
WALLBOARD JOINT CEMENT INDUSTRY
Open File Report 89-2
July, 1989
by Ken A. Phillips
Chief Engineer
Arizona Department of Mines and Mineral Resources
1502 West Washington
Phoenix, Arizona 85007
This is a preliminary report,
Subject to technical and
Editorial revision.
Arizona Department of Mines and Mineral Resources
Open File Report 89-2
July, 1989
INDUSTRIAL MINERALS IN ARIZONA’S
WALLBOARD JOINT CEMENT INDUSTRY
By Ken A. Phillips, Chief Engineer
ABSTRACT
This report briefly describes Arizona’s wallboard joint cement industry and, in more detail, the
specifications and quantities of industrial minerals consumed.
The Arizona wallboard joint cement manufacturing industry uses a larger quantity of industrial
minerals as extender pigments and functional fillers than any other Arizona industry. Minerals used in-clude
limestone, talc, mica, kaolin clay, attapulgite clay, and perlite. More than 50 million pounds of
minerals, with a value in excess of 2 million dollars, are imported by Arizona annually for use in manu-facturing
joint cement. Since a number of these minerals are not currently produced here a market for
local material exists.
Development of mines and production of these minerals in Arizona would aid the state’s economy.
Additionally, these minerals could be available to manufacturers in Arizona, California, and other
southwestern states at lower prices due to savings in transportation costs.
Acknowledgements
I would like to take this opportunity to ex-press
my appreciation to all of the Arizona
manufacturers who provided assistance and in-formation.
Without their cooperation the data to
assemble this report would not have been avail-able.
Tim Whitney, Murco Wall Products, Buck-eye
W. H. (Bill) Cox, Western Stucco Products,
Glendale
Jim Jones, Highland Products, Phoenix
K. O. (Nick) Tuhus, Gold Bond Building
Products, Phoenix
A special thank you is extended to Tim
Whitney listed above for taking the time to pro-vide
an education on joint cement manufactur-ing
and raw materials and for his review of this
chapter.
Development Potential in Arizona
An opportunity for development of Arizona
mineral deposits exists because few of these
minerals are currently mined in Arizona, despite
the likelihood that significant deposits occur
within the state. Further, there are additional
markets in the Southwest and potential export
markets.
Wallboard Joint Cement
The wallboard joint cement manufacturing
industry in Arizona uses a larger quantity of in-dustrial
minerals as functional fillers than any
other industry in the stare. For the purpose of
this report, products such as wallboard texture
coatings and ceiling texture spray coating are
included.
Wallboard joint cement is known by a
number of common names including ‘dry wall
mud,’ ‘tape joint compound, ‘joint cement,’ and
‘mud.’ It is the sealer and adhesive used to at-tach
joint tape to the junctions between sheets of
gypsum wallboard on walls and ceilings. Wall-board
is also called gypsum board and sheet
rock®. In addition to being used with joint tape
to hide or conceal joints, it is also used to cover
nail and screw heads and to cover the wall-board’s
paper surface to provide an equally ab-sorbent
and uniform surface prior to the applica-tion
of a decorative coating such as paint.
Wallboard joint cement is produced in a
number of different varieties for use in various
applications. Types such as chemically setting,
lightweight, topping, and all-purpose are all
made for differing applications or environ-mental
conditions of application. Wallboard
joint cement is manufactured as both a wet
ready-to-use product and as a dry powder that
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must be mixed with water at the job site prior to
application.
Wall and ceiling texture compounds are
manufactured for application to wallboard sur-faces
after taping and sealing to provide a deco-rative
texture for walls and ceilings. Wall tex-ture
coatings are nearly always subsequently
painted, while ceiling texture coatings do not
necessarily require painting.
Wallboard joint cement is a mixture of raw
materials. It generally consists of a starch or la-tex
(for wet ready-to-use products) or vinyl
resin (for dry mix products) binder, water, eth-ylene
glycol (to prevent freezing or control dry-ing
time), various dryers and preservatives, and
mineral fillers. The mineral fillers make up the
major portion of the product. Wall and ceiling
texture coatings additionally contain hiding
pigments such as titanium dioxide. Ceiling coat-ings
usually contain coarsely ground expanded
polystyrene particles. Ceiling coatings requiring
acoustical properties may contain expanded
vermiculite or popped perlite.
Ready-to-use wallboard joint cement is
packaged in four gallon boxes weighing 50
pounds, one gallon pails, and pails weighing 62
pounds. Dry mix joint cement is packaged in
25-pound bags. Lightweight joint cement made
in Arizona is packaged in four-gallon boxes
weighing 40 pounds.
Functional Fillers
Functional fillers for wallboard joint ce-ment
can, for the purpose of discussion, be di-vided
into two groups; those which impart some
useful property such as strength or sag resis-tance
to the final mixture and those that fill
space, add bulk, and extend the usefulness of the
other constituents. Ground limestone is the most
common bulk filler in joint cement, but many
white, non water-soluble mineral fillers could be
used in its place. Functional fillers used include
mica, talc, kaolin clay, attapulgite clay, and
popped perlite.
ARIZONA’S JOINT CEMENT MANU-FACTURING
INDUSTRY
Arizona’s joint cement manufacturing in-dustry
consists of four plants producing over 1.5
million boxes (average weight per box: 50
pounds or the equivalent in pails and dry mix
material) of joint cement and wall texture coat-ing
a year. These plants manufacture about 80
percent of the joint cement consumed in the
state. Most, if not all, of the remaining 20 per-cent
is shipped in from California. Two plants
produce joint cement only, while the other two
produce both joint cement and wall/ceiling tex-ture
coatings. All of the plants are Arizona op-erations
of out-of-state corporations. A major
gypsum wallboard manufacturer operates one
plant.
Wallboard joint cement is used in new and
remodeling construction only. Thus the eco-nomic
health of that industry directly affects the
quantity of joint cement consumed. Further it is
used when gypsum wallboard is used as an inte-rior
wall or ceiling covering. Neither wood or
vinyl paneling nor lathe and plaster require joint
cement. Within the last few years, actual pro-duction
of joint cement in Arizona has ranged
from slightly under 1 million boxes to over 2
million.
Industrial Minerals in Joint Cement
Arizona joint cement manufacturers con-sume
at least six different industrial minerals as
functional fillers. They are listed in Table No. 1
along with typical annual consumption and
prices. Typical price ranges are given to help
estimate the size of the market. The lowest
prices are often those paid by warehouses and
the largest bulk users, while the highest prices
are often in quantities of single pallet loads and
materials obtained through distributors’ ware-houses.
Material may be supplied in bulk rail
cars, bulk trucks, ‘super sacks’ (bulk bags that
hold from 1000 to 3000 pounds), or in 50-pound
paper bags. The larger consumers often negoti-ate
prices and delivery contracts directly with
the mining-processing-supplier company at
terms lower than published prices.
The industrial minerals used in joint cement
manufactured in the state are described in the
remainder of this chapter. All are very finely
ground and must conform to detailed specifica-tions.
Some are interchangeable in certain uses.
One Arizona producer of wallboard joint
cement has in the past mined and ground raw
mineral materials, particularly mica, themselves.
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Although not presently operating their own
mines, they hope to produce some of their raw
materials again and market excess production to
other manufacturers.
Those interested in developing new sources
of these minerals should be fully aware of the
idiosyncrasies of the industrial minerals indus-try.
Suppliers of minerals to the industry are ex-pected
to provide considerable technical data
and support to potential consumers.
Commodity Quantity Consumers’ prices
(tons)
minimum
per ton
maximum
per ton
Limestone 20,725 48 78
Mica 1,968 238 270
Talc 1,270 102 124
Kaolin 538 134 960
Attapulgite
Clay 410 208
Perlite 30
Table 1. Typical annual consumption of Ari-zona’s
wallboard joint cement manufacturers.
Calcium Carbonate
The most commonly used filler in joint ce-ment
is calcium carbonate, primarily as fine
ground white limestone or marble. It is ground
much- finer than 325 mesh with the mean parti-cle
size being in the range of 10 to 15 microns.
Calcium carbonate supplies volume solids or
bulk at a low cost. At about $0.025 per pound
(or 62 to 75 cents per 50 pound box), it is the
cheapest ingredient in joint cement.
Calcium carbonate’s tendency to ‘frost’ or
‘chalk’ when repeatedly exposed to moisture
does not present a problem in joint cement. Joint
cement is seldom used in exterior applications
and is always protected by painting.
The three most important specifications for
ground calcium carbonate to be used in joint
cement are whiteness, chemical stability, and
particle size. Whiteness is important because the
finished product must be white to avoid show-ing
through paint coating applied over the joint
cement, especially since most interior walls in
residential construction are painted white or
very light colors. Whiteness should be above 90.
Fine and consistent particle size is important to
manufacturing joint cement that applies evenly.
The necessity for chemical stability is somewhat
nebulous. Limestone or marble that can be
ground for joint cement use must be free of wa-ter
soluble or water absorbable foreign minerals
that could cause tape adhesion problems or the
appearance of blemishes in the wall coating.
Common clays are typical impurities that should
be avoided. However, the limestone or marble
need not be pure CaCO3. Dolomitic limestone
or marble can be used if white. Many white sili-cate
minerals such as a feldspar or pyrophyllite
could also be used, but must compete on a price
basis with ground limestone.
Nearly all of the ground limestone used by
Arizona joint cement manufacturers is imported
from Lucerne Valley in southern California. The
cost of shipping ground limestone from Lucerne
Valley to Phoenix area manufacturers is ap-proximately
$25.00 per ton in bulk trucks.
Calcium carbonate used in joint cement is
typically one of two average particle sizes; 10
microns or 15 microns. (US sieve mesh 325 is
approximately 44 microns.) A typical specifica-tion
for fine ground calcium carbonate used in
the manufacture of wallboard is shown below:
Typical chemical analysis (Calcium carbonate)
CaCO3 - minimum 97-98%, MgCO3 - 1%, Acid in-soluble
2%
Typical particle size distribution
Mean particle size - 10 microns
Percentage by weight finer than:
Microns %
44 90 min.
20 50
15 40
5 13
2 8
Typical physical characteristics
Dry brightness 91
Gallons per pound 0.0445
Pounds per gallon 22.5
Specific gravity 2.71
Moisture less than 0.20%
Ph Factor 9.5
Oil absorption 8
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Kaolin
Kaolin, also known as kaolin clay or kao-linite,
and sometimes referred to as china clay or
aluminum silicate, is a functional filler that is
white, has some hiding power, provides some
strength, and ties up water to control drying. Its
hiding power is a result of the delaminated clay
particles piling up and overlapping. As a filler it
is chemically inert. It also improves spreadabil-ity.
Ground kaolin used by Arizona joint ce-ment
manufacturers is imported from northern
California. The cost of shipping ground kaolin
from northern California to Phoenix area manu-facturers
ranges from $35.00 to $40.00 per ton
in truckload quantities.A typical specification
for fine ground kaolin is shown below:
Typical chemical analysis
Al2O3 38.8%
SiO2 45.2%
Na2O 0.05-0.3%
TiO2 0.6-1.7%
CaO 0.02%
Fe2O3 0.3-0.9%
MgO 0.03%
K2O 0.05-0.2%
Loss on ignition 13.6-14.2%
Typical particle size distribution (Kaolin)
Retention on 325 mesh screen 0.15%
Mean particle size 4.8 microns (Equivalent
spherical diameter)
Percentage by weight finer than:
Microns %
20 99+
10 85
5 50
2 21
Typical physical characteristics
Physical form Highly pulverized powder
Dry brightness 79-82
Specific gravity 2.58
Moisture less than 1.0%
Ph factor 3.5-5.10
Oil absorption 30-35
Refractive index 1.56
Bulk density (loose) 24 lb/cu ft
” ” (tamped) 45 lb/cu ft
Attapulgite Clay
Attapulgite clay is a gelling clay used as a
thickener and/or thixotropic agent. It provides
sag control, aids in spreadability of the final
product, and the holding of ingredients in sus-pension.
Nearly all of the attapulgite clay used by
Arizona joint cement manufacturers is imported
from the Georgia-Florida area of the southeast-ern
United States. The cost of shipping attapul-gite
clay from the southeast U.S. to Phoenix
area manufacturers is approximately $90.00 per
ton in truckload quantities.
Mica
Ground mica is used in joint cement where
its platy structure and high aspect ratio (area:
thickness) provides a number of useful proper-ties.
It prevents packing of the other fillers, adds
strength to the applied layer on the wallboard,
and aids in shrink and cracking control. Mica
for use in joint cement must be white when
ground and free of dark particles of other miner-als.
Air ground or micronized muscovite is most
commonly used, but dry ground sericite or mus-covite
has been occasionally used. Both musco-vite
and sericite have been mined in Arizona in
the past for use in joint cement.Most of the
ground muscovite mica used by Arizona joint
cement manufacturers is imported from North
Carolina. The cost of shipping ground musco-vite
mica from North Carolina to Phoenix area
manufacturers is in the range of $80 to $110 per
ton in truckload quantities.A typical specifica-tion
for fine ground mica is shown below:
Typical chemical analysis
Theoretical chemical formula H2KAl3(SiO4)3
Typical physical characteristics
Color white and lustrous
Particle shape very thin and platy
Particle size distribution
+60 mesh nil
-60 +100 mesh 1.5%max
-100 +200 mesh 10.0% min
-325 mesh 50.0% min
Chemical activity essentially inert except
to H2
Loss on ignition 4-5%
Specific gravity 2.8-3.0
Moisture 0.25%
Oil absorption g/mg 80.0
Refractive index 1.58
Bulk density (apparent loose) 14 lbs/cu ft
Hardness (MOHS) 2.5
Ph 5.75
Surface area m2/g 6.64
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Ground pyrophyllite could be used in joint
cement in the same manner as mica.
Talc
Talc is less expensive than mica and can
replace some of the mica in joint cement where
it provides similar properties. Its platy grain
structure helps keep the mixture in suspension
and aids workability.
Most of the ground talc used by Arizona
joint cement manufacturers is imported from
Montana, while some is still supplied from cen-tral
California. The cost of shipping ground talc
to Phoenix area manufacturers ranges from $30
to $55 per ton in truckload quantities.A typical
specification for fine ground talc is shown be-low:
Typical chemical analysis
SiO2 61.5 –63.1%
MgO 31.0 – 32.9%
Al2O3 0.93 – 2.37%
CaO 0.19 – 3.90%
Fe2O3 1.00 – 1.30%
K2O 0.01 – 0.13%
TiO2 0.05 – 0.20%%
Loss on
ignition 5.50 – 6.20%
Typical particle size distribution (talc)
Retention on 100 mesh screen nil
Retention on 200 mesh screen nil
Retention on 325 mesh screen 2.0%
Typical physical characteristics
Dry brightness 80-84
Specific gravity 2.70
Apparent density 28.7 lbs/cu ft
Tapped density 56.5 lb/cu ft
Perlite
Perlite is used in a ground, then expanded
form, as a lightweight filler. Bag-house-fines
from perlite expanding (also called popping)
plants are also used. Perlite used in wallboard
joint cement must be very white when ex-panded.
It is used in place of some of the cal-cium
carbonate.
Diatomaceous Earth (Diatomite)
Diatomaceous earth or diatomite is a filler
primarily used in joint cement for its low effec-tive
density in light weight products. Because of
the physical structure of the individual particles
making up diatomaceous earth, they lay in a
random, three-dimensional pattern that stiffens,
reinforces and improves the durability of the
final product. The variety of shapes also pro-vides
low density. The effective density of dia-tomaceous
earth fillers is among the lowest of
any mineral fillers at 1.98 to 2.33 grams per cu-bic
centimeter. Diatomaceous earth occupies up
to 30 percent more volume per pound than most
other filler minerals.
Diatomaceous earth is not currently used by
any of the Arizona wallboard joint cement
manufacturers.
Feldspar
White feldspar, if locally available, could
replace limestone as the primary filler in wall-board
joint cement. Increased grinding costs
would have to be compensated for by reduced
transportation costs.
Wollastonite
Wollastonite could be used in place of some
mica and limestone in wallboard joint cement
where the acicular shape of the ground wollas-tonite
particles would provide many of the same
properties provided by ground mica.
Conclusions
Arizona’s wallboard joint cement industry
uses the largest quantity of industrial minerals
as fillers of any industry in Arizona. All of these
are currently imported into Arizona. Occur-rences
of most of these minerals, in particular,
limestone, mica, kaolin, perlite, pyrophyllite,
and diatomaceous earth, are known in Arizona.
The consumption of these minerals in joint ce-ment
might be sufficient to justify a small spe-cialized
multi-mineral producer operating a
number of small mines, each producing a spe-cific
mineral, but utilizing a common grind-ing/
processing plant.
Additionally, many of the minerals used in
joint cement have nearly the same specification
as those used in Arizona’s paint industry, al-though
the quantities used in paint are much
smaller. Thus a multi-mineral producer could
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produce for more than one Arizona industry.
Further, southern California is a large market for
industrial minerals in wallboard joint cement as
well as paint. It is expected that investigation of
other industries in Arizona and southern Cali-fornia
will yield consumption data that will pro-duce
totals of sufficient quantities to justify de-velopment
of new mines in Arizona.
